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People Are More Willing to Dismiss Evidence From Psychology Than Brain Science

posted Feb 25, 2015, 9:52 AM by Resty Manapat

Imagine
a politician from your party is in trouble for alleged misdemeanors. He’s been
assessed by an expert who says he likely has early-stage Alzheimer’s. If this
diagnosis is correct, your politician will have to resign, and he’ll be
replaced by a candidate from an opposing party.

This
was the scenario presented to participants in a new study by Geoffrey Munro and
Cynthia Munro. A vital twist was that half of the 106 student participants read
a version of the story in which the dementia expert based his diagnosis on
detailed cognitive tests; the other half read a version in which he used a
structural MRI brain scan. All other story details were matched, such as the
expert’s years of experience in the field, and the detail provided for the
different techniques he used.

Overall,
the students found the MRI evidence more convincing than the cognitive tests.
For example, 69.8 percent of those given the MRI scenario said the evidence the
politician had Alzheimer’s was strong and convincing, whereas only 39.6 percent
of students given the cognitive tests scenario said the same. MRI data was also
seen to be more objective, valid and reliable. Focusing on just those students
in both conditions who showed skepticism, over 15 percent who read the
cognitive tests scenario mentioned the unreliability of the evidence; none of
the students given the MRI scenario cited this reason.

In
reality, a diagnosis of probable Alzheimer’s will always be made with cognitive
tests, with brain scans used to rule out other explanations for any observed
test impairments. The researchers said their results are indicative of naive
faith in the trustworthiness of brain imaging data. “When one contrasts the very
detailed manuals accompanying cognitive tests to the absences of formalized
operational criteria to guide the clinical interpretation of structural brain
MRI in diagnosing disease, the perception that brain MRI is somehow immune to
problems of reliability becomes even more perplexing,” they said.

What
about the students with a very strong political identity for whom the
diagnostic evidence was therefore particularly unwelcome? The researchers found
that the gap between the perception of MRI and cognitive testing was largest
for this group. This is because, when the students were highly motivated to
disbelieve the diagnosis of Alzheimer’s, those told about the cognitive tests
were very dismissive, but those told about the MRI scans showed similar levels
of trust to their less partisan peers. The authors said this suggests we are
more willing to discount unwelcome psychological evidence than we are to
discount brain-based evidence.

These
new results add to past findings showing people’s bias for neuroscience and
other “hard” sciences and against psychology. For example,medical students think their psychology lectures are “soft and
fluffy”;students think psychology is less important than the other natural
sciences;children rate psychological questions as easier than chemistry or
biology questions; and expert testimony supporting an insanity defenseis seen as less convincing when delivered by a psychologist than a
psychiatrist. Another line of research suggests people areparticularly influenced by images of brain scans, although
recent attempts havefailed to replicate this finding.

The
researchers called for their work to be extended into other contexts, and for
the allure of neuroscience to be probed more deeply. “The need for the general
public to accurately evaluate the scientific methods used by psychologists is
especially relevant to real-world situations,” they said, “in which strongly
held values, beliefs, or identification with specific groups renders people
particularly likely to discount psychological evidence.”

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